Pavement markers (e.g., paints, tapes, and individually mounted articles) guide and direct motorists and pedestrians traveling along roadways and paths. Pavement markers are used on, for example, roads, highways, parking lots, and recreational trails, to form stripes, bars and markings for the delineation of lanes, crosswalks, parking spaces, symbols, legends, and the like. Paint was a preferred pavement marking for many years. The formed or applied traffic lines created by these pavement markers form a part of the road surface and are thus subjected to the wear and destructive action of traffic.
Pavement markers consisting of preformed tapes or strips are well known in the art to be advantageous in comparison to the conventional pavement marking paints. Preformed pavement markers offer significant advantages over paint, such as increased visibility, retroreflectance, improved durability, and temporary and/or removable marking options. Preformed marking tapes are typically formed from a composite structure comprising a support base of calendared rubber compound, a self-adhesive layer, and a topcoat anti-wear layer incorporating anti-skid material and retroreflective elements. Such a composite structure is disclosed in many patents, such as, for example, U.S. Pat. Nos. 3,782,843, 3,935,365, 3,399,607, 4,020,211, 4,117,192, 4,990,024, and 4,988,555 all of which are incorporated by reference in their entirety.
Polyurethane resins have been used in the topcoat layer for many years due to their high tensile and tear strength coupled with abrasion resistance (see, for example, U.S. Pat. No. 5,643,655, incorporated by reference in its entirety.). Pavement marking tapes including a polyurethane topcoat have a high capacity to be deformed, high permanent set, and low elastic return while providing durability. These pavement marking tapes deform readily into intimate contact with irregular pavement surfaces, absorb the energy of wheel impacts without fracture and avoid the stretch-return action that has been found to loosen marking tapes from a roadway pavement. Typical examples of such pavement marking tapes can be found, for example, in U.S. Pat. Nos. 4,117,192 and 4,990,024, both of which are incorporated by reference in their entirety. A negative aspect of such a deformable marking tape relates to its low mechanical properties, in particular, low tensile strength and too high a level of elongation.
Various polyurethane topcoats are known. One such polyurethane topcoat is described in U.S. Pat. No. 5,126,170. The process described in this patent involves reacting a polyol, a polyaspartic ester amine, and a polyisocyanate to form a coating including urea-modified polyurethane.